1. Field of the Invention
The present invention relates to a resin-sealed semiconductor device.
2. Description of the Related Art
As well known, a semiconductor power device such as an intelligent power module for use in a power source incorporated in an inverter device for household electrical or industrial appliances, comprises primary components such as power chips and control ICs provided on the upper surface of a substrate which is supported in an enclosure, and generally sealed with a curing resin material for protection against an external environment.
FIG. 10 is a plan view schematically showing a conventional resin-sealed semiconductor power device before being sealed with a resin material. The semiconductor power device 80 has an IGBT 83 as a power chip, a FWDi (Free Wheel Diode) 84, and a control IC 85 provided on an insulating substrate 82 which is supported in an enclosure 81. In addition, provided on the upper main surface of the insulating substrate 82 is a milliohm resistor 86 of a plate-like shape. The enclosure 81 is equipped with a set of external connection terminals 87 which is insert formed. Also, bonding wires are provided on the upper main surface of the insulating substrate 82, as well as circuit patterns, for electrical connection between the components but not shown in FIG. 10 for simplicity of the description.
FIG. 11 is a longitudinal cross sectional view of the milliohm resistor 86 taken along the line Cxe2x80x94C of FIG. 10. The milliohm resistor 86 is arranged of generally a raised form of its plate-like material which is anchored at both ends (denoted by 86b) to the insulating substrate 82. Accordingly, a space 90 is provided as defined between the milliohm resistor 86 and the upper main surface 82a of the insulating substrate 82. A raised portion 86a of the milliohm resistor 86 extends in parallel with the insulating substrate 82.
The components on the insulating substrate 82 are sealed with a curing resin 92 for protection against the external environment as shown in FIG. 12. However, as the milliohm resistor 86 and the enclosure 81 of the semiconductor power device 80 are located adjacent to each other in the resin sealing step, the space 90 defined between the milliohm resistor 86 and the insulating substrate 82 may hardly be filled with the resin 92 but bubbles of air. When the air escapes from the space 90 during the curing of the resin, it may produce a void(s) 92a at the surface in the resin 92. Otherwise, the air trapped in the space 90 may decline the thermal conductivity of the milliohm resistor 86 and thus prevent the milliohm resistor 86 from releasing a redundancy of heat.
It is an object of the present invention to provide a resin-sealed semiconductor device which allows unwanted air to be bled out steadily and readily from the space defined between the resistor of a plate-like shape and the insulating substrate in the resin sealing step.
A resin-sealed semiconductor device in an aspect of the present invention includes a resistor of a plate-like form placed and anchored at both ends onto the upper main surface of a substrate, providing a space between the resistor and the substrate. The primary components including said resistor on the substrate are sealed with a curing resin material. In this resin-sealed semiconductor device, the resistor includes a portion which is opposite to the substrate and defines the space with the substrate, and an aperture is formed in said portion for communication between the space and the upper side of the resistor.
Accordingly, an air can be prevented from entrapping in the space during the resin packaging step. As a result, the generation of voids in the resin when cured can be prevented. Also, as its aperture and space are steadily filled with the resin, the resistor remains high in the thermal conductivity and can thus be inhibited from generating overheat.
Said aperture is located at substantially the center of said portion of the resistor. This allows unwanted air to be effectively bled from the space.
A roughness of a surface facing the substrate (that is, a lower surface) in said portion of the resistor is set to 2S or lower. This also allows unwanted air to be effectively bled from the space with much ease.